The severity of a respiratory alkalosis is determined by the difference between the actual pCO2 and the expected pCO2
The actual pCO2 is the measured value from the blood gas results.
If no metabolic acid-base disorder is present, a pCO2 of 40 mmHg is taken as the reference point (ie the expected pCO2).
If a metabolic disorder is present, respiratory compensation will produce a new reference value of pCO2 for comparison. The expected pCO2 can be estimated using the formula in Section 5.5 (for metabolic acidosis) or Section 7.5 (for metabolic alkalosis).